(1) Field of the Invention
The present invention generally relates to a storage assembly and to a method for making the same and more particularly, to a metal hydride storage assembly which efficiently and selectively receives/stores and emits hydrogen gas and which may be relatively easily and cost effectively manufactured and scaled to readily accommodate a wide variety of diverse storage requirements.
(2) Background of the Invention
Metal hydride material is known to efficiently receive/store and selectively emit hydrogen gas. Accordingly, such material has been used in vehicular applications in which a fuel cell assembly is used to operate a vehicle. Although various types of fuel cells exist, a common type of fuel cell uses hydrogen gas in combination with another material (e.g., gasoline) to produce electricity. The hydrogen gas is typically provided by a reformation system and is communicated to the fuel cell assembly by a controller, according to a sensed demand. In order to improve response and efficiency, metal hydride material has been used as a buffer and, in this configuration, is operatively effective to allow a hydrogen powered type of fuel cell assembly ready or quick access to hydrogen when a large demand is placed upon the fuel cell assembly, thereby reducing the overall response time and allowing the fuel cell to operate at peak efficiency and to deliver the desired output power level.
The metal hydride buffer is further operatively effective to receive hydrogen gas produced by the reformation system and to allow the reformation system to continue to efficiently produce relatively large amounts of hydrogen even when a relatively small demand is placed upon the fuel cell assembly. Such a sinking type buffer has been found to increase the overall operating efficiency of the hydrogen producing reformation system since the buffer allows the reformation system to operate at a relatively large or production capacity (e.g., the reformation system operates most efficiently when it is producing large amounts of hydrogen), even when all of the produced hydrogen is not used by the fuel cell assembly. Hence, one of the principal benefits of such a buffer is to store the hydrogen which would be otherwise wasted if the required load or amount of required hydrogen drops at a faster rate than the rate at which the reformation system may reduce its output, and to provide hydrogen when the amount of required hydrogen increases at a faster rate than the rate at which hydrogen may be supplied by the reformation system.
Particularly, the metal hydride material, in the form of a powder, is usually contained within several tubes which are disposed within a manifold storage assembly which may be generally round. The storage assembly is selectively heated in order to cause the contained material to absorb hydrogen and is selectively cooled in order to cause the material to emit or de-absorb the previously received hydrogen and to allow the emitted hydrogen to be communicated to the fuel cell assembly.
While the foregoing storage assembly does provide some of the desired hydrogen buffering, it suffers from some undesirable drawbacks. That is, by way of example and without limitation, the foregoing metal hydride storage assembly does not readily transfer the applied energy (e.g., the heat or the cold energy) to the contained metal hydride material, thereby causing the storage assembly to operate inefficiently and to undesirably reduce the overall response time of the assembly (i.e., the time in which hydrogen is emitted or absorbed after such absorption or emission is requested by the generation of the energy in the form of heat or cold). Attempts to increase the heat transfer attribute of the storage assembly include machining or removing portions of the walls of the tubes and/or placing one or more conductive members within each of the tubes. These attempts undesirably increase the cost and complexity of the storage assembly and cause or increase the likelihood of damage to the assembly as well as increasing the amount of required maintenance.
Further, the foregoing storage assembly is relatively difficult to manufacture, requiring a relatively large amount of uniquely shaped components which must be intricately coupled in a certain manner, and the foregoing storage assembly suffers from compaction type failures (i.e., as the contained material is repeatedly heated and cooled or cycled, the metal hydride particles become smaller and migrate to various locations within the assembly where, upon again becoming heated, they swell and structurally damage the storage assembly). Attempts to address these compaction type failures undesirable increase cost and complexity of the assembly by requiring the use of a segmented member in each of the tubes and/or undesirably thickening the walls of the tube.
Moreover, the foregoing metal hydride storage assembly is not readily and cost effectively scaleable (i.e., not capable of being readily adapted to contain varying amounts of material) since the manifold storage assembly has a fixed amount of tubular reception apertures which contribute to the overall space requirements of the assembly even when they fail to operatively contain material, the prior assembly undesirably requires a relatively large amount of storage or mounting space within the vehicle, and the prior assembly is not easily adapted to be manufactured in a variety of sizes.
There is therefore a need for a new and improved metal hydride storage assembly and a method for making such a new and improved assembly which overcomes some or all of the previously delineated disadvantages of prior assemblies.